1. Field of the Invention
The present invention relates to a structure regarding compression of the image data and production of a thumbnail image in an electronic device provided with a photographing mechanism capable of taking a picture of a still image and a moving image, an image processing apparatus, and a data structure.
2. Description of the Related Art
In recent years, it's often the case that a camera is incorporated in an electronic device such as a personal computer, a PDA, and a cellular phone, so that such an electronic device can take a picture of a still image and a moving image. These electronic devices are configured by a camera module and other part (a host module). The camera module is provided with a solid-state image sensing device. Converting the light inputted in this solid-state image sensing device into an electric signal and applying the necessary image processing to this electric signal, the image data is produced. Then, the obtained image data is transmitted to the host module. The host module takes charge of a telephone functionality and a PDA functionality, saves the image data transmitted from the camera module in a recording medium, and then, displays this image data to a display unit such as an LCD. The structure and the signal processing used for taking a picture of the still image and the moving image refers to a structure and the signal processing of a device used exclusively by photographing such as a conventional digital camera and digital video camera. Such a conventional art is disclosed in JP-A-9-147095 and JP-A-10-155137 or the like.
FIG. 9 is a pattern diagram showing an example of the structure and the signal processing of the electronic device, in which a camera using the conventional art is incorporated. A camera cellular phone 201 of the conventional art is configured by a camera module 202 and a host module 203. The processing to be carried out in the camera module 202 is loosely described below. In step 205, a solid-state image sensing device such as a CCD converts a light into an electric signal, and further, it digitizes this electric signal. In step 206, the image data is constructed from the output data of the digitized solid-state image sensing device and the image data is outputted in step 207. In the same way, the processing to be carried out in the camera module 203 is loosely described below. At first, in step 209, receiving the image data outputted from the camera module, this image data is temporarily saved in a frame buffer memory. Next, in step 210, reading out the image data saved in the frame buffer memory, this image data is compressed in a format such as a JPEG and in step 211, reading out the image data saved in the frame buffer memory, the thumbnail data of this image data is produced. In the meantime, the thumbnail is an image produced remarkably decreasing a resolution of the original image data and it is mainly produced to be displayed on a small display screen of the cellular phone and the digital camera. The compression image data is saved in a data recording medium such as a flash memory and a memory card in step 212, the thumbnail data is displayed on the display unit such as a LCD in step 213, and further, the thumbnail may be saved in the data recording medium together with the compression image data.
However, if the electronic device such as the camera cellular phone and the camera PDA is produced by the art that has been developed depending on the device used exclusively by taking a picture, such as a digital camera and a digital video camera, distinctive problems occur. According to one of these problems, the data amount to be transmitted between the camera module and the host module should be kept within the bus width of a transmission path. If the resolution of the solid-state image sensing device of the camera module is increased, it seems preferable that the image data is compressed in advance in the camera module so as to keep the data amount to be transmitted between the camera module and the host module in the bus width of the transmission path. The data communication amount between the modules should be decreased not only in the case of the solid-state image sensing device having high resolution but also in the case of taking a picture of the moving image.
Moreover, in the electronic device having the camera incorporated therein, considering the load of the processing apparatus of the host module, it is believed that the thumbnail is also produced in the camera module. This is particularly needed in taking a picture of the moving image because the image data about 10 to 30 frames per second are continuously transmitted from the camera module to the host module upon taking a picture of the moving image and the load of the host module is made larger if the compression, production of the thumbnail, saving into the recording medium, and display of the thumbnail about these all image data are performed in the host module. Further, it is so because the electronic device having the camera incorporated therein should spare its processing ability not only to the functionality regarding these photographing but also to the functionalities peculiar to the host module such as a telephone function and a schedule function.
For the reasons mentioned above, it seems preferable that the compression of the image data and the production of the thumbnail image of this image data are carried out in the camera module in the electronic device having the camera incorporated therein. However, assuming that the thumbnail production functionality is simply moved from the host module to the camera module to be incorporated therein, it is necessary for the camera module to have a large frame buffer memory in order to temporarily save the entire of the image data of one frame. This frame buffer memory causes rising of the cost and the size of the camera module and more this problem becomes serious, particularly the more the resolution of the image data is increased.